Jeff Passan

With Friday's news that the independent Atlantic League -- as part of its new partnership with Major League Baseball -- will implement several rules changes for 2019, let's take a closer look at four of the major proposals and how likely they are to make their way from independent baseball to the major leagues:

Robot umpires

The rule change: Using TrackMan radar to help umpires call balls and strikes.

What it would mean: Robot umps! According to ESPN Stats & Information data, the correct call rate on balls and strikes in 2018 was 91.1 percent. How robot umpires could be implemented is yet to be determined, but the goal is obviously to improve the accuracy of ball and strike calls. Keep in mind, however, that the technology is far from perfect.

As a basic example, the generic strike-zone graphics you see on TV broadcasts don't adjust the size of the strike zone to the size of the batter, such as Aaron Judge compared with Jose Altuve. Until the players start wearing sensors on their jerseys, there is still guesswork involved at the top and bottom of the zone.

Potential impact on baseball: Well, Jeff Mathis would probably be out of a job. The average MLB game in 2018 featured 297 pitches, with 157 of those called strikes or balls. Given an incorrect call rate of 8.9 percent, that means about 14 pitches per game are missed -- with a certain percentage of those ball/strike calls influenced by catchers like Mathis who are good at framing pitches. That skill set would become less valuable -- or, presumably, have no value at all. That could lead to a return of better-hitting catchers, at least if they can still throw and work with a pitching staff. Of course, maybe even the art of calling a game would disappear once we got to robot pitch selections.

Likeliness MLB would adopt: Strong ... though not immediately. In recent years, MLB commissioned a study in a number of major league stadiums to test the viability of using radar systems to track strikes. Because of imperceptible changes in weather, crowd size or other factors that ever-so-slightly moved the systems' components, the would-be strike zone actually changed location game by game. The argument, of course, is that game-by-game strike-zone changes already happen with different umpires manning home plate -- and that's a salient point. What baseball doesn't want is technology, whose greatest attribute is its consistence and relative infallibility, failing an early test and losing momentum. When there are robot umps -- and there will be -- it will be Version 3.0 or 4.0. This is 1.0.

Banning the shift as we know it

The rule change: Two infielders must be on each side of the second-base bag when the pitch is released, with the penalty being the pitch is called a ball.

What it would mean: The end of the shift.

Potential impact on baseball: The majority of shifts are against left-handed batters, especially slow left-handed sluggers who pull everything while trying to hit home runs. According to Sports Info Solutions, there were nearly 35,000 shifts employed in 2018 -- counting only balls in play when the shift was on -- a 30 percent increase from 2017 and 93 percent increase from 2014. The five most shifted hitters were Kyle Seager, Matt Carpenter, Freddie Freeman, Anthony Rizzo and Matt Olson. The only right-handed batter in the top 30 was Edwin Encarnacion. SIS estimated that Carpenter lost the most hits to the shift in 2018: a net total of 23 (33 lost, 10 gained). Give him an additional 23 hits and his batting average increases from .257 to .298. (All data from "The Bill James Handbook.")

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Overall, SIS estimated that the shift saved 592 runs in 2018 -- an average of 19.7 per team -- as the batting average on grounders and short liners went down. Russell Carleton of Baseball Prospectus, however, wrote up a study last May that came to a much different conclusion. He concluded that while singles do go down against a full shift, walks go up (and home runs go up slightly as well), outweighing the benefits of eliminating some base hits. Obviously, the analytics departments within teams haven't reached the same conclusions as Carleton given the continued increase in shifts, but maybe the assumed benefits of the shift aren't so cut-and-dried. Just don't tell Matt Carpenter.

Likeliness MLB would adopt: This is a hard one. The shift is dynamic, not just in the infinite forms it can take but the number of opinions it generates. Hard-boiled scouts like it because they believe in the sanctity of restriction-free defensive alignments. Some analysts abhor it because it only compounds the lack of action in modern baseball. Other analysts revere it because it can be so efficient at generating outs. Plenty more scouts scoff at it as data run amok. The study by Carleton -- who now works for the Mets -- was brilliant in its rigor and the counterintuitiveness of its conclusion. Even more complex are the unintended consequences of a rule change. If pre-pitch shifts are limited, will defensive players be sent in motion as the pitch is being thrown? Does baseball really want to open a Pandora's box of restrictiveness on account of some singles being lost? Ultimately, that's in the hands of commissioner Rob Manfred, and he's the one who has broached publicly the possibility of ending the shift.

Batter minimum for relievers

The rule change: A three-batter minimum for pitchers (a rule change MLB and the players' association are considering for 2020).

What it would mean: Fewer within-inning pitching changes, speeding up the pace of the game.

Potential impact on baseball: There were 1,145 relief appearances in 2018 of one batter faced and another 1,143 of two batters. The top five pitchers last season in relief appearances of one or two batters:

As you might expect, all are lefties. In fact, the only righties in the top 25 were Steve Cishek and Luis Garcia. The good news is MLB may be already trending away from the one-batter appearances -- in part because starters are throwing fewer innings and you need more outs from relievers who can't be wasted on one-batter appearances. In 2015, there were 1,398 one-batter appearances.

With a three-batter minimum, there will be some lefty specialists who will be out of work, or at least in much less demand. That in turn could help left-handed batters, who face more of the one-batter relievers. Left-handed hitters had a .753 OPS against right-handed pitchers in 2018, but a .668 OPS against left-handed pitchers.

Likeliness MLB would adopt: 100 percent. MLB wants this to help limit pitching changes and speed up games. The players' association doesn't mind it because even if it's killing a job class, the union believes the market for relief pitching will remain robust and what it's getting as part of the deal to bring in the three-batter minimum is a worthwhile trade.

New distance from mound to home plate

The rule change: Increasing the distance from the pitching rubber to home plate from 60 feet, 6 inches to 62 feet, 6 inches (in the second half of the season).

What it would mean: The pitching rubber has been at 60 feet, 6 inches since 1893. The height of the mound has changed and the definition of the strike zone has changed several times, but the distance from the rubber to home plate has remained a constant for 126 years. Increasing the pitching distance would certainly have an impact on strikeouts as MLB officials look to stem the rising tide of whiffs.

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Potential impact: Unknown -- but potentially drastic, at least in the short term as pitchers adjust after throwing at one distance since they were teenagers. Not only would batters have a slightly longer reaction time to those blazing fastballs, but pitchers would have to tweak their breaking balls and off-speed pitches to get them to work at the longer distance. All this could lead to a huge increase in offense -- more hits, more home runs, more walks -- and longer games because of the increase in runs.

We don't have a lot to go on here, but consider these numbers from 2018:

Batters against fastballs of 92 to 93 mph: .272/.361/.474

Batters against fastball of 95 to 96 mph: .246/.330/.406

When the height of the mound was lowered in 1969, the average runs per game increased from 3.42 in 1968 to 4.07 (it was also an expansion year). A similar 19 percent increase in scoring would increase the average runs per game from 4.45 in 2018 to 5.30 -- which would be higher than the peak season of the steroid era, 5.14 runs per game in 2000. It will certainly be fascinating to see the results in the Atlantic League.

Likeliness MLB would adopt: Slim but certainly not none. It's not just the iconic numbers of 60 feet, 6 inches. Moving the mound up or down already has a drastic enough effect (see 1968 vs. 1969). Shifting it back could fundamentally alter a number of the game's elements. First: the ability to pitch effectively. Every single pitcher in the world has thrown from a 60-6 distance since their teen years. Breaking balls are calibrated to move at 60-6. Changeups sink at a certain point. Maybe it's an overestimation to think this -- and it's what makes a test like the Atlantic League's important -- but the potential for enormous change feels real. Pitchers and hitters would have to recalibrate themselves, learn how to adjust to something seemingly minuscule but in reality incredibly difficult.

The Atlantic League experiment may prove how long that recalibration and adjustment take -- and whether it's actually viable enough to at least consider testing out in the affiliated minor leagues before potential major league adoption.

More potential changes: Aside from those major rules changes, the Atlantic League will also eliminate mound visits except for pitching changes or injuries, increase the size of the bags, and reduce the time between innings and pitching changes.

The Atlantic League already employs a pitch clock, which the commissioner's office had discussed unilaterally employing for 2019 until recently backing off that proposal until 2022 if it reaches some common ground with the union on other rules changes.

The pitch clock would obviously speed up the pace of the game. Grant Bisbee of SB Nation compared a full game from 1984 to one from 2014, two games featuring similar totals of pitches, baserunners and batters. The 1984 game lasted 2 hours, 31 minutes; the 2014 game lasted 3 hours, 6 minutes. There were nine more minutes of commercials in 2014, but as Grant wrote, "Time between pitches is the primary villain" of the longer game now. The time between "inaction" pitches -- there were 146 such pitches in the 1984 game, 144 in 2014 -- increased 25 minutes, or about an extra nine seconds between pitches.

Pitchers would have to adopt to a pitch clock, especially power-throwing relievers who tend to take more time between pitches. But former major leaguers Mark Teixeira and Carlos Pena have both talked in recent weeks about how a clock could also hurt batters, who would have less time to think and collect themselves between pitches.

So the impact here is unknown -- except the pace of the game would definitely improve.